Enhancing the Oxidation Stability of Polydivinylbenzene Films via Residual Pendant Vinyl Passivation

Abstract

Polydivinylbenzene (PDVB) is a thermally stable, optically transparent, crosslinked polymer that until recently has been difficult to synthesize as a thin film. With the recent demonstration of initiated chemical vapor deposition (iCVD) of thin PDVB films, a renewed interest in the material properties of PDVB has developed. In particular, attention is now focused on its oxidation pathways and long‐term stability under the desired application use conditions. Here, we report on the thermal and environmental stability of PDVB films and show that unreacted pendant vinyl groups drive polymer oxidation upon exposure to either air or light. We demonstrate that such vinyls can be effectively passivated by a simple ex‐situ thermal annealing at ca. 300 °C in inert atmosphere that induces an 87% reduction of the PDVB oxidation rate in air and slows light (λ=405 nm) induced oxidation by 56%. While the thermal annealing is less effective at preventing oxidation under higher energy (λ = 365 nm) UV light, we demonstrate that this aging pathway is based on the presence of reactive oxygen species rather than traditional photo‐oxidation. Vinyl removal through ex‐situ thermal annealing improves the chemical stability of iCVD PDVB to continuous air (over 500 days) or light (70 hours) exposure and offers a simple option to improve its environmental aging resistance which is important for long‐term protective applications.

Biomimetic Fabrication of Janus Fabric with Asymmetric Wettability for Water Purification and Hydrophobic/Hydrophilic Patterned Surfaces for Fog Harvesting

“…Similarly, an absorption peak of a carbonyl group was also observed at 1740 cm –1 in Figure S4, which generated a full-chain structure. Therefore, the oxidation of PDVB caused by UV radiation leads to the presence of carbonyl-containing functional groups and hydroxyl groups, resulting in a reduction in WCA. , …”

Cross‐linked polystyrene and polydivinylbenzene release significant amounts of carbon monoxide and hydrogen at ambient temperature

“…Cross‐linked polystyrene (CL‐PS), or styrene‐divinylbenzene copolymer, and polydivinylbenzene (PDVB) are widely used as the platform materials for various functional resins that are used for the separation of the mixtures of chemical and biological products and as plastic blast materials 1–7 . These polymers have unreacted pendant vinyl groups, which undergo aging, or oxidation with air, giving rise to the formation of OH and (CO)CH 3 groups 8 . This aging process has been known to proceed even at room temperature and becomes accelerated as temperature increases.…”

“…Here, based on the literature report, 8 the chemically adsorbed O 2 means by the O atoms that exist in the forms of COH and (CO)CH 3 groups within the polymer, which were produced as a result of handling the polymers in air. Consistent with this, the released amounts of CO and H 2 were much higher upon using O 2 as the carrier gas (Figure S1c).…”

“…The two contrasting TGA profiles of PDVB and alumina clearly confirm that in the case of PDVB the weight initially increases, although slightly, and subsequently decreases slightly. Based on the literature report, 8 we attribute the weight increase to the chemical adsorption of O 2 on the polymer by formation of OH and  (CO)CH 3 groups by the reaction between the pendant vinyl groups and O 2 . Thus, O 2 initially reacts with the pendant vinyl groups of PDVB to form the oxidized groups even at 40 °C, and the oxidized forms undergo decomposition, liberating CO and H 2 .…”